FGFR-1 IS REQUIRED FOR EMBRYONIC GROWTH AND MESODERMAL PATTERNING DURING MOUSE GASTRULATION

Experiments in amphibians have implicated fibroblast growth factors (F GFs) in the generation and patterning of mesoderm during embryogenesis . We have mutated the gene for fibroblast growth factor receptor 1 (fg fr-1) in the mouse to genetically dissect the role of FGF signaling du ring development. In the absence of fgfr-1 signaling, embryos displaye d early growth defects; however, they remained capable of gastrulating and generating mesoderm. The nascent mesoderm of fgfr-1 homozygous mu tant embryos differentiated into diverse mesodermal subtypes, but meso dermal patterning was aberrant. Somites were never generated and axial mesoderm was greatly expanded at the expense of paraxial mesoderm. Th ese results suggest that FGFR-1 transduces signals that specify mesode rmal cell fates and regional patterning of the mesoderm during gastrul ation.